920 OYSTERS, AND ALL ABOUT THEM. 



out the East as a sovereign cure for heart-disease, ague, 

 and indigestion. According to Rajah Sourindro, pearl- 

 dust not only heals "the ills that flesh is heir to," but 

 " ministers to a mind diseased." Outwardly applied, it 

 extirpates leprosy and stops bleeding; taken inwardly, it is 

 a " sure antidote to poison, drives away all imaginary fears, 

 and removes all bodily pain." Used as snuff, it dissipates 

 cataract, and imparts a brilliant lustre to the eyes. 



But with the advance of science these crude fancies 

 and curious fables have gradually passed away. So far as 

 the lights of our present knowledge can guide us in solving 

 these difficult problems of the origin and formation of 

 Pearls, Mr. Streeter submits the following rational explana- 

 tion : 



"The oyster lies at the bottom of the sea, at an angle 

 more or less considerable, but is generally inclined to the 

 sea bottom at about 20 to 25. The shell is usually open 

 about i^ inches, to admit the entrance of water, its owner's 

 natural sustenance, and the mantle is spread out over the 

 horny outside lips of the shell. Respiration is carried on 

 by means of the gills, and any organic particles in the 

 water which bathes these vascular organs are transferred 

 to the mouth. Scientists have taught us that ' haemo- 

 globin,' or the colouring matter of the blood in the animal 

 kingdom, is the agent, that owing to its great affinity for 

 oxygen, extracts that supporter of life from the air inhaled. 

 Of the agent that extracts the oxygen from water, either 

 salt or fresh, we are, however, still untaught. The water 

 is admitted between the ' mantle lobes ' into the ' pallial 

 chambers,' where it is oxygenated : the oyster evidently 

 retains a considerable amount of gas within itself, many 

 shells being discovered by the divers, simply by the 



